I made the dumbest mistake the other day. My gas furnace just would not turn on. I freaked out and read online about heater issues. I read that if a heater does not turn on, something major must be wrong. It means the heater overheated and then quit. It also could mean the heater has a big part that is malfunctioning. I immediately called my local HVAC contractor to come in and make this expensive heater repair. I was prepared for almost a $400 bill for the furnace. I was all set to do what it took to have quality heating. A part of me was worried and anticipating having to buy another furnace system. The HVAC professional did not even look at my furnace. He immediately went over to my thermostat and inspected it. He took the thermostat apart and then told me my batteries were dead. I thought that surely could not be the issue. After replacing the batteries, the heating system turned on just fine. The heater did not make any scary sounds or threaten to turn off. It was just batteries in the thermostat that was the problem. The HVAC guy charged me $100 for that issue. He charged me for the time he spent getting to my house and his labor. Changing batteries is considered labor? I was really peeved after paying that bill. I am never going to make this mistake again. Not only was it a pricey one, but I felt like such an idiot in front of my HVAC professional.